Drone to DEM Methods of UAS data acquisition

and assimilation into GIS

Robert K. Garst

Project Goals

• Capture aerial images with a model aircraft

• Create a dense point cloud of the subject area to produce the following products

• Digital Elevation Model

• Orthophoto Mosaic

UAS User Groups

• Business Users

• Apply for exemption

• Operate with FAA airworthiness certificate

• Both require COA

• Public Entities

• Certificate of Waiver or Authorization

• Recreational Users

• Hobbyist Rule

Commercial Use

• What is Commercial Use?

• Selling media recorded from UAS

• Using a UAS for contract services

• Provide professional services with UAS

• How to operate UAS with commercial purpose?

• Apply for Exception, and COA

• Obtain an FAA airworthiness certificate, and COA

Public Entities

• Governments, law enforcement, public colleges and universities

• Requires only a COA

• Processing time takes approximately 60 days

• A COA has a predetermined term

• Online application

Recreational Users

• No FAA authorization or COA required

• Cannot exceed 400 feet in altitude

• Do not fly near restricted airspace or air fields

• Yield to all other aircraft

• Join the Academy of Model Aeronautics!

UAS Components

• Aerial Platform

• Camera System

• Data Link

• Ground Control

Aerial Platform

• Multicopter design

• Vertical takeoff and landing

• Lower flight speeds

• Tight hardware and software integration with other components onboard aircraft

• Stable camera platform

http://joshanon.com

Camera System

• Small, lightweight payload

• 12MP resolution

• Standard “Fisheye” lens replaced

• Three axis gimbal mount

Lens Focal Point

35 mm Equivelant

HorizontalFOV

Stock Lens 2.92 mm 16.21 mm 123º

New Lens 5.40 mm 29.97 mm 62º

Stock Fisheye lensHFOV: 123 degrees

Replacement lensHFOV: 62 degrees

Camera System

• Small, lightweight payload

• 12MP resolution

• Standard “Fisheye” lens replaced

• Three axis gimbal mount

Lens Focal Point

35 mm Equivelant

HorizontalFOV

Stock Lens 2.92 mm 16.21 mm 123º

New Lens 5.40 mm 29.97 mm 62º

Data Link• Autonomous control

• Interface through iPad Ground Station software

• Fail safe - home coordinates and redundant radio set with traditional controller

Ground Control

• Provides horizontal and vertical control for the model

• 101 reference points collected

• 10 used to georeference model

• 91 reserved for verification

http://www.leica-geosystems.us

UAS Demonstration

Flight Plan Details

• 8 flight strips spanning the neighborhood

• Minimum 60% image overlap required

• Actual sequential overlap: 90%

• Actual flight strip overlap: 70%

• Flown 300 feet above the surface

• Flown at noon for best lighting

• 521 raw photographs

Raw Photograph Overlay

Wild HeerbruggStereo Plotter A8

http://www.officemtt.com

Agisoft Photoscan Pro Workspace

Photoscan View Points

Ground Control

• 10 points used for georeferencing the model

• 91 points reserved for verifying model

Horizontal Error Vertical Error Combined Error

Absolute Error of Point Cloud

Digital Terrain Model

Photoscan View Points

Orthophoto distortionExample #1

Orthophoto distortionExample #2

Orthophoto resolution: 1 inch per pixel

USDA

Disadvantages and Advantages

• Disadvantages

• Resource intensive

• Artifacts present at large map scales

• Advantages

• Produce three products - LAS Dataset, DEM, Orthophoto

• Inexpensive

• Quick turn around time

Acquire Photographsof Subject Area

Align Images and Create “View Points”

Build SparsePoint Cloud

Build DensePoint CloudBuild Polygonal Mesh

Register Modelinto FL East

Coordinate System

Rebuild DensePoint Cloud

Rebuild Polygonal Mesh

LAS Dataset Digital Elevation Model Orthophoto

Apply Photographs to Poly Mesh

GIS

Drone to DEM Methods of UAS data acquisition

and assimilation into GISRobert K. Garst

rgarst88@gmail.com